Update README.md

README.md

@@ -19,10 +19,11 @@ pip3 install keep-exporter
 
 
 ## Usage
+If you do not supply a username or password before running it, you will be prompted to input them.
 ```
 keep_export [OPTIONS]
 Options:
   -d, --directory TEXT  Output directory for exported notes
   -u, --user TEXT       Google account email (environment variable 'GKEEP_USER')
   -p, --password TEXT   Google account password (environment variable 'GKEEP_PASSWORD')
-```
+```